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Wilfred T Tysoe - One of the best experts on this subject based on the ideXlab platform.
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low Temperature shear induced tribofilm formation from dimethyl disulfide on copper
ACS Applied Materials & Interfaces, 2011Co-Authors: Octavio Javier Furlong, Peter V. Kotvis, Brendan P. Miller, Wilfred T TysoeAbstract:The frictional properties of a sliding copper-copper interface exposed to dimethyl disulfide (DMDS) are measured in UHV under conditions at which the Interfacial Temperature rise is <1 K. A significant reduction in friction is found from the clean-surface values and sulfur is found on the surface and below the surface in the wear scar region by Auger spectroscopy. Because the Interfacial Temperature rise under the experimental conditions used to measure friction is very small, tribofilm formation is not thermally induced. The novel, low-Temperature tribofilm formation observed here is ascribed to a shear-induced intermixing of the surface layer(s) with the subsurface region as suggested using previous molecular dynamics simulations. Although the tribofilm contains predominantly sulfur, a small amount of carbon is also found in the film.
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the surface and tribological chemistry of carbon disulfide as an extreme pressure additive
Wear, 2000Co-Authors: J Lara, Peter V. Kotvis, K Surerus, M E Contreras, J L Rico, Wilfred T TysoeAbstract:Abstract The reaction of carbon disulfide with clean iron was investigated for Temperatures between 623 and 776 K and pressures between 10 and 30 Torr. Film growth is limited by the thermal decomposition of CS 2 at the growing interface and the activation energy for this process is 12.4±1.0 kcal/mol. The nature of the resulting film is analyzed using Raman and Mossbauer spectroscopies and by X-ray diffraction, where it is found that the film consists of a non-stoichiometric ferrous sulfide and also incorporates a carbide. This result is in accord with the tribological data where the Interfacial Temperature in the plateau region of a plot of seizure load vs. additive concentration is ∼1460 K, the melting Temperature of FeS. The seizure load increases substantially when the additive concentration exceeds ∼2 wt.% of sulfur and, since carbide formation was detected in the film, this is ascribed to the formation of an iron carbide at higher additive concentrations.
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surface chemistry of chlorinated hydrocarbon lubricant additives part i extreme pressure tribology
Tribology Transactions, 1998Co-Authors: Peter V. Kotvis, Wilfred T TysoeAbstract:Chlorinated hydrocarbons are commonly added to a base lubricating fluid when it is used for extreme-pressure (EP) lubrication of ferrous metals. It is demonstrated here that the Interfacial Temperature in the EP regime varies linearly with the applied load in a pin and v-block testing apparatus and that Temperatures in excess of ˜ 1000 K can be attained. Thermally decomposing chlorinated hydrocarbon vapors on iron heated to these Temperatures (1) shows that a film consisting of an iron chloride which incorporates small carbon particles (˜50A) is formed. In this paper, tribological measurements at extreme pressures and the corresponding analyses of the rubbing surfaces and wear particles also indicate that this film, formed from the chlorinated lubricant reacting with these surfaces, is the critical antiseizure material at less severe EP loads and Interfacial Temperatures less than ˜1000 K.
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surface chemistry of chlorinated hydrocarbon lubricant additives part ii modeling the tribological interface
Tribology Transactions, 1998Co-Authors: T J Blunt, Peter V. Kotvis, Wilfred T TysoeAbstract:In Part I (1), the concept of “Type I” antiseizure behavior for chlorinated hydrocarbons in extreme-pressure (EP) lubrication of ferrous metals was introduced; Interfacial Temperature measurements and surface analyses revealed that a solid lubricating layer consisting of ferrous chloride (FeCl2) and carbon prevents seizure and acts as a solid lubricant at less than ˜1000 K. In this paper, careful measurement of the film growth and removal rates successfully rationalizes this tribological behavior. Thermodynamic calculations also show that iron carbides are favored at higher decomposition Temperatures. Analysis of films formed from the thermal decomposition of carbon tetrachloride (CCl4) and chloroform (CHCl3) at ˜1000 K using Mossbauer spectroscopy demonstrates that iron carbide is indeed formed in this case; tribological measurements also confirm this material as critical antiseizure material at high loads in “Type II” tribological behavior for chlorinated hydrocarbons with ferrous metals.
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the surface chemistry of chloroform as an extreme pressure lubricant additive at high concentrations
Tribology Letters, 1995Co-Authors: Wilfred T Tysoe, T J Blunt, J Lara, K Surerus, Peter V. KotvisAbstract:Carbon tetrachloride is an extremely good extreme-pressure (EP) lubricant additive at low concentrations ( 4 wt% chlorine) in accord with the idea that a higher melting point carbide film can be formed. It has been shown previously that asymptotes in the plot of removal rate versus applied load correspond to melting of the Interfacial anti-seizure film. When using 9.0 wt% chlorine from chloroform as the additive, a drastic increase in removal rate is found at an Interfacial Temperature of ~940 K corresponding to the melting of FeCl2 and an additional asymptote is evident at ~1500 K due to the melting of Fe3C in accord with the thermodynamic and Mossbauer results.
Khellil Sefiane - One of the best experts on this subject based on the ideXlab platform.
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effect of ambient Temperature and relative humidity on Interfacial Temperature during early stages of drop evaporation
Physical Review E, 2016Co-Authors: Yuki Fukatani, Daniel Orejon, Yasuyuki Takata, Khellil Sefiane, Yutaku Kita, Jungho KimAbstract:Understanding drop evaporation mechanisms is important for many industrial, biological, and other applications. Drops of organic solvents undergoing evaporation have been found to display distinct thermal patterns, which in turn depend on the physical properties of the liquid, the substrate, and ambient conditions. These patterns have been reported previously to be bulk patterns from the solid-liquid to the liquid-gas drop interface. In the present work the effect of ambient Temperature and humidity during the first stage of evaporation, i.e., pinned contact line, is studied paying special attention to the thermal information retrieved at the liquid-gas interface through IR thermography. This is coupled with drop profile monitoring to experimentally investigate the effect of ambient Temperature and relative humidity on the drop Interfacial thermal patterns and the evaporation rate. Results indicate that self-generated thermal patterns are enhanced by an increase in ambient Temperature and/or a decrease in humidity. The more active thermal patterns observed at high ambient Temperatures are explained in light of a greater Temperature difference generated between the apex and the edge of the drop due to greater evaporative cooling. On the other hand, the presence of water humidity in the atmosphere is found to decrease the Temperature difference along the drop interface due to the heat of adsorption, absorption and/or that of condensation of water onto the ethanol drops. The control, i.e., enhancement or suppression, of these thermal patterns at the drop interface by means of ambient Temperature and relative humidity is quantified and reported.
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the effect of wall thickness and material on marangoni driven convection in capillaries
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2015Co-Authors: Cosimo Buffone, Khellil Sefiane, Christophe MinettiAbstract:Abstract We present results of an experimental investigation of Marangoni convection for an evaporating meniscus in open air pinned at the mouth of a capillary tube. Four different liquids have been studied: ethanol, methanol, acetone and, for the first time, also FC-72. This experimental configuration has been studied before by the present authors and others. However, it is the first time that the effect of the capillary tube thickness and material is experimentally investigated. In particular, the study considered the same internal diameter for all the tubes (1 mm) and three borosilicate external diameters (1.4, 2, and 3 mm) as well as one polycarbonate (1.25 mm) and one sapphire (3 mm). These three tube materials were chosen for their very different thermal properties and their optical transparency. The evaporation rate is measured by tracking the second meniscus receding inside the capillary tube while the first one is pinned at the tube mouth. It was found that the evaporation rate is influenced more by the thermal conductivity of the tubes than the wall thickness. An infrared camera has also been employed to measure the Interfacial Temperature at the meniscus pinned at the tube mouth and also along the wall of the tube close to the tube mouth. In addition, a heat transfer analysis has been performed at the tube mouth along with a mass transfer analysis which allowed the evaluation of the Temperature of the meniscus interface and the evaporation rate, respectively, and comparing these results with the measured ones. The deviation found is maximum 65% between measured and calculated Temperature differences between wall and meniscus and 6.7% for the evaporation rate. The results are qualitatively assessed in the light of those obtained for evaporating sessile drops and the trends found are similar.
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on evaporation rate and Interfacial Temperature of volatile sessile drops
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2009Co-Authors: Victor Starov, Khellil SefianeAbstract:Abstract A theoretical description of the evaporation of sessile drops is proposed. The linear dependency of the evaporation rate on droplet's base radius is described as well as the Interfacial Temperature. The analysis shows that most of evaporation is indeed concentrated near the contact line as demonstrated by experiments from literature. The evaporative cooling induced by evaporation results in a non-uniform Temperature profile along the interface, being colder on the apex and hotter near the contact line. This result is counter-intuitive. It is the reason why the physical explanations are provided. Interfacial Temperature gradient leads to Marangoni thermocpaillary driven flow within the drop.
Peter V. Kotvis - One of the best experts on this subject based on the ideXlab platform.
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low Temperature shear induced tribofilm formation from dimethyl disulfide on copper
ACS Applied Materials & Interfaces, 2011Co-Authors: Octavio Javier Furlong, Peter V. Kotvis, Brendan P. Miller, Wilfred T TysoeAbstract:The frictional properties of a sliding copper-copper interface exposed to dimethyl disulfide (DMDS) are measured in UHV under conditions at which the Interfacial Temperature rise is <1 K. A significant reduction in friction is found from the clean-surface values and sulfur is found on the surface and below the surface in the wear scar region by Auger spectroscopy. Because the Interfacial Temperature rise under the experimental conditions used to measure friction is very small, tribofilm formation is not thermally induced. The novel, low-Temperature tribofilm formation observed here is ascribed to a shear-induced intermixing of the surface layer(s) with the subsurface region as suggested using previous molecular dynamics simulations. Although the tribofilm contains predominantly sulfur, a small amount of carbon is also found in the film.
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the surface and tribological chemistry of carbon disulfide as an extreme pressure additive
Wear, 2000Co-Authors: J Lara, Peter V. Kotvis, K Surerus, M E Contreras, J L Rico, Wilfred T TysoeAbstract:Abstract The reaction of carbon disulfide with clean iron was investigated for Temperatures between 623 and 776 K and pressures between 10 and 30 Torr. Film growth is limited by the thermal decomposition of CS 2 at the growing interface and the activation energy for this process is 12.4±1.0 kcal/mol. The nature of the resulting film is analyzed using Raman and Mossbauer spectroscopies and by X-ray diffraction, where it is found that the film consists of a non-stoichiometric ferrous sulfide and also incorporates a carbide. This result is in accord with the tribological data where the Interfacial Temperature in the plateau region of a plot of seizure load vs. additive concentration is ∼1460 K, the melting Temperature of FeS. The seizure load increases substantially when the additive concentration exceeds ∼2 wt.% of sulfur and, since carbide formation was detected in the film, this is ascribed to the formation of an iron carbide at higher additive concentrations.
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surface chemistry of chlorinated hydrocarbon lubricant additives part i extreme pressure tribology
Tribology Transactions, 1998Co-Authors: Peter V. Kotvis, Wilfred T TysoeAbstract:Chlorinated hydrocarbons are commonly added to a base lubricating fluid when it is used for extreme-pressure (EP) lubrication of ferrous metals. It is demonstrated here that the Interfacial Temperature in the EP regime varies linearly with the applied load in a pin and v-block testing apparatus and that Temperatures in excess of ˜ 1000 K can be attained. Thermally decomposing chlorinated hydrocarbon vapors on iron heated to these Temperatures (1) shows that a film consisting of an iron chloride which incorporates small carbon particles (˜50A) is formed. In this paper, tribological measurements at extreme pressures and the corresponding analyses of the rubbing surfaces and wear particles also indicate that this film, formed from the chlorinated lubricant reacting with these surfaces, is the critical antiseizure material at less severe EP loads and Interfacial Temperatures less than ˜1000 K.
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surface chemistry of chlorinated hydrocarbon lubricant additives part ii modeling the tribological interface
Tribology Transactions, 1998Co-Authors: T J Blunt, Peter V. Kotvis, Wilfred T TysoeAbstract:In Part I (1), the concept of “Type I” antiseizure behavior for chlorinated hydrocarbons in extreme-pressure (EP) lubrication of ferrous metals was introduced; Interfacial Temperature measurements and surface analyses revealed that a solid lubricating layer consisting of ferrous chloride (FeCl2) and carbon prevents seizure and acts as a solid lubricant at less than ˜1000 K. In this paper, careful measurement of the film growth and removal rates successfully rationalizes this tribological behavior. Thermodynamic calculations also show that iron carbides are favored at higher decomposition Temperatures. Analysis of films formed from the thermal decomposition of carbon tetrachloride (CCl4) and chloroform (CHCl3) at ˜1000 K using Mossbauer spectroscopy demonstrates that iron carbide is indeed formed in this case; tribological measurements also confirm this material as critical antiseizure material at high loads in “Type II” tribological behavior for chlorinated hydrocarbons with ferrous metals.
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the surface chemistry of chloroform as an extreme pressure lubricant additive at high concentrations
Tribology Letters, 1995Co-Authors: Wilfred T Tysoe, T J Blunt, J Lara, K Surerus, Peter V. KotvisAbstract:Carbon tetrachloride is an extremely good extreme-pressure (EP) lubricant additive at low concentrations ( 4 wt% chlorine) in accord with the idea that a higher melting point carbide film can be formed. It has been shown previously that asymptotes in the plot of removal rate versus applied load correspond to melting of the Interfacial anti-seizure film. When using 9.0 wt% chlorine from chloroform as the additive, a drastic increase in removal rate is found at an Interfacial Temperature of ~940 K corresponding to the melting of FeCl2 and an additional asymptote is evident at ~1500 K due to the melting of Fe3C in accord with the thermodynamic and Mossbauer results.
Roman O Grigoriev - One of the best experts on this subject based on the ideXlab platform.
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the effect of gas phase transport on marangoni convection in volatile binary fluids driven by a horizontal Temperature gradient
International Journal of Heat and Mass Transfer, 2020Co-Authors: Tongran Qin, Roman O GrigorievAbstract:Abstract Recent experimental and numerical studies of convection in confined layers of volatile binary liquids with a free surface subjected to a horizontal Temperature gradient have observed a reversal in the direction of Interfacial flow as the concentration of air in the vapor space above the liquid is decreased. These observations suggest that transport in the gas phase has a significant effect on the balance between thermocapillary and solutocapillary stresses, the competition between which determines the flow direction. In order to develop a quantitative description of the flow reversal, we use the two-sided (liquid/gas) transport model introduced previously to obtain approximate analytical solutions for the Interfacial Temperature and composition of the liquid, hence predict thermocapillary and solutocapillary stresses, and the flow direction. Therefore, our solutions provide useful guidelines for choosing the optimal binary coolants composition and operating conditions for thermal management applications. Despite the complex nature of this problem, we have found that the mass transport in the gas phase is effectively one-dimensional and independent of the flow in moderate to large aspect-ratio cavity for sufficiently low Temperature gradients, which allows this problem to be simplified and solved analytically in a sequential manner. Our theoretical predictions agree well with the results of numerical simulations, which indicates that the analytical analysis captures the essential physics of the problem.
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a numerical study of buoyancy marangoni convection of volatile binary fluids in confined geometries
International Journal of Heat and Mass Transfer, 2018Co-Authors: Roman O GrigorievAbstract:Abstract A horizontal Temperature gradient can cause a flow in a layer of liquid with a free surface via several different mechanisms. The most universal one is due to thermocapillary stresses that arise due to the Temperature dependence of surface tension. For binary liquids, the flow can also be driven by solutocapillary stresses that arise due to the dependence of surface tension on the composition of the liquid. For some binary liquids, such as water-alcohol mixtures, solutocapillary stresses are primarily due to phase change (e.g., differential evaporation or condensation of the two components), and these two mechanisms can counteract each other. A recent experimental study (Li and Yoda, 2016) has demonstrated that the flow direction can be reversed by changing the amount of air present inside the experimental apparatus. To understand how the presence of air affects the Interfacial stresses, we have developed and implemented numerically a comprehensive two-sided transport model, which accounts for transport of heat, mass, and momentum in both phases and phase change across the interface and is able to reproduce the experimental results. The detailed analysis of these results shows that air tends to suppress phase change and hence solutocapillary stresses. Removing the air enhances phase change, instead suppressing the variation in the Interfacial Temperature and hence thermocapillary stresses.
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convection evaporation and condensation of simple and binary fluids in confined geometries
ASME 2012 Third International Conference on Micro Nanoscale Heat and Mass Transfer, 2012Co-Authors: Tongran Qin, Roman O GrigorievAbstract:Rayleigh-Benard and Marangoni convection in a layer of a homogeneous fluid with a free surface in the absence of phase change is a classic (and extensively studied) problem of fluid mechanics. Phase change has a major effect on the convection problem. Most notably, significant latent heat generated at the free surface as a result of phase change can dramatically alter the Interfacial Temperature, and hence, the thermocapillary stresses. Furthermore, differential evaporation in binary fluids can lead to considerable variation in the concentration field, producing solutocapillarity stresses, which can compete with thermocapillarity and buoyancy.This talk describes numerical studies of convection in alcohol and alcohol-water mixtures due to a horizontal Temperature gradient in the presence of phase change. We illustrate how the composition of the liquid and the presence of non-condensable gases (e.g., air) can be used to alter the balance of the dominant forces. In particular, by adding or removing air from the test cell, the direction of the flow can be reversed by emphasizing either the thermocapillary or the solutocapillary stresses.© 2012 ASME
Yasuyuki Takata - One of the best experts on this subject based on the ideXlab platform.
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evaporation kinetics of pure water drops thermal patterns marangoni flow and Interfacial Temperature difference
Physical Review E, 2018Co-Authors: Tejaswi Josyula, Zhenying Wang, Alexandros Askounis, Daniel Orejon, Sivasankaran Harish, Yasuyuki Takata, Pallab Sinha Mahapatra, Arvind PattamattaAbstract:We report a systematic study of the role of Marangoni convection in the evaporation kinetics of pure water drops, considering the influence of the heating regime and surface wettability. Marangoni flows were induced via heating under constant wall Temperature (uniform heating) and constant heat flux (local heating) regimes below the drops. To visualize the thermal patterns emerging during the evaporation, we employed infrared thermography and we captured the evolution of the drop profile with a CCD camera to follow the evaporation kinetics of each drop. We observed a strong correlation between the Temperature difference within the drop and the evolution of the drop shape during different modes of evaporation (i.e., constant radius, angle, or stick-slip) resulting in different Marangoni flow patterns. Under uniform heating, stable recirculatory vortices due to Marangoni convection emerged at high Temperature, but they faded at later stages of the evaporation process. On the other hand, in the localized heating case, the constant heat flux resulted in a rapid increase in the Temperature difference within the drop capable of sustaining Marangoni flows throughout the evaporation. Surface wettability was found also to play a role in both the emergence of the Marangoni flows and the evaporation kinetics. In particular, recirculatory flows in drops on hydrophobic surfaces were stronger when compared to flows on hydrophilic surfaces for both uniform and local heating. To quantify the effect of the heating mode and the importance of Marangoni flows, we calculated the evaporative flux for each case and found it to be much higher in the localized heating case. Evaporative flux depends on both diffusion and natural convection of the vapor phase to the ambient. Hence, we estimated the Grashof number for each case and found a strong relation between natural convection in the vapor phase and heating regime or Marangoni convection in the liquid phase. Subsequently, we demonstrate the limitation of the previously reported diffusion-only model in describing the evaporation of heated drops.
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effect of ambient Temperature and relative humidity on Interfacial Temperature during early stages of drop evaporation
Physical Review E, 2016Co-Authors: Yuki Fukatani, Daniel Orejon, Yasuyuki Takata, Khellil Sefiane, Yutaku Kita, Jungho KimAbstract:Understanding drop evaporation mechanisms is important for many industrial, biological, and other applications. Drops of organic solvents undergoing evaporation have been found to display distinct thermal patterns, which in turn depend on the physical properties of the liquid, the substrate, and ambient conditions. These patterns have been reported previously to be bulk patterns from the solid-liquid to the liquid-gas drop interface. In the present work the effect of ambient Temperature and humidity during the first stage of evaporation, i.e., pinned contact line, is studied paying special attention to the thermal information retrieved at the liquid-gas interface through IR thermography. This is coupled with drop profile monitoring to experimentally investigate the effect of ambient Temperature and relative humidity on the drop Interfacial thermal patterns and the evaporation rate. Results indicate that self-generated thermal patterns are enhanced by an increase in ambient Temperature and/or a decrease in humidity. The more active thermal patterns observed at high ambient Temperatures are explained in light of a greater Temperature difference generated between the apex and the edge of the drop due to greater evaporative cooling. On the other hand, the presence of water humidity in the atmosphere is found to decrease the Temperature difference along the drop interface due to the heat of adsorption, absorption and/or that of condensation of water onto the ethanol drops. The control, i.e., enhancement or suppression, of these thermal patterns at the drop interface by means of ambient Temperature and relative humidity is quantified and reported.